(02/14/11) Lecture by Kevin Ahern of Oregon State University discussing Biochemistry Basics in BB 451. See the full course at oregonstate.edu This course can be taken for credit (wherever you live) via OSU’s ecampus. For details, see ecampus.oregonstate.edu Download Metabolic Melodies at www.davincipress.com Related courses include BB 350 – oregonstate.edu BB 450 – oregonstate.edu BB 100 – oregonstate.edu DNA Replication/Repair/Recombination III 1. Initiation of replication in E. coli occurs at a specific site on the E. coli genomic DNA, known as OriC, in the cell’s circular chromosome. The OriC site contains three repeats of an AT rich sequence near some sequences bound by the DNA A protein. 2. Replication initiation begins with binding of the several copies of the DNA A protein to the OriC site. Bending and wrapping of the DNA around DNA A proteins causes the AT-rich sequences noted above to become single-stranded. 3. Next, the DNA BC complex binds the DNA B protein (helicase) to each of the single strands in opposite orientations. The DNA C protein is released in the process (I said this backward in class). Next, SSB and primase bind the exposed single-stranded regions and cause DNA A protein to be released. The primases begin synthesizing RNA primers (remember – 5′ to 3′ RNA synthesis only also) in opposite directions on each strand. The primases DO NOT require a pre-existing primer to function. 4. Note that replication is bi-directional – two replication forks …
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